Heat control device



Aug. 1, 1944. L w. cooK 2,354,910

HEAT CONTROL DEVICE Original Filed Aug. 28, 1942 2 o L69 17 J4 Z6 0 o Inventor: Leonard W. Cook H I5 AttoT-Tweu.

Patented Aug. 1, 1944 HEAT CONTROL DEVICE Leonard W. Cook, Stratford, Coma, assignor to General Electric Company, a corporation of New York Original application August 28, 1942, Serial No.

456,509. Divided and this application December 19, 1942, Serial No. 469,567

Claims.

My invention relates to manually operated switches and more particularly to such switches for use with electrically heated blankets and the like, and its object is to provide an improved manually operated switch which is simple in construction, cheap to manufacture, and reliable in operation.

This application is a division of my copending application Serial No. 456,509, filed August 28, 1942.

My invention will be better understood from the following description when taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 is a front elevation view of one form of a heat control device embodying my improved manually operated switches; Fig. 2 is a sectional view of the device taken along line 2--2 of Fig. 1 and looking in the direction indicated by the arrows; Fig. 3 is a back view of the device with the back cover removed; Fig. 4 is a sectional View of the device taken along the line 1-4 of Fig. 3 and looking in the direction indicated by the arrows; Fig. 5 is the same view as Fig. 4 except the line switch is in its closed position; and Fig 6 diagrammatically il- :a blanket control system embodying my new control device.

Referring to the drawing, my control device 1 comprises a housing or base 8 of suitable insulating material, :such for example as plastic or other molded material. This housing 8 is so formed that "it constitutes the front and sides of my improved control device. The back of the housing 8 is arranged to be covered by a cover 8 that is fastened to the housing 8 by screws l0.

,An escutcheon plate ll of suitable material, such as sheet brass, covers a portion of the front and bottom of the housing 8, this escutcheon plate being held in place by an extension I! at the bottom thereof which extends upwardly along a portion of the back of the housing 8 below the cover 9 and by means of a metallic bushing l8 which extends through an opening in the front of the housing 8 and the escutcheon i I. One end H of the bushing I3 is enlarged and polygonally shaped and is inserted in a similar shaped opening in the inner surface of the housing so as to prevent rotation of the bushing. The other end ii of the bushing I3 is spun over so as to hold the escutcheon plate ll firmly against the outer surface of the housing 8. The plate ll also'constitutes means for conducting the heat from the therein follows more closely the ambient temperature changes.

The inner surface of the bushing I8 is threaded, and in threaded engagement therewith is a round hollow steel shaft I! having a portion of its outer surface threaded for engagement with the inner threaded surface of the bushing l3. Aknob l8 of suitable insulating material, such as plastic, is attached to the portion of the shaft H which protrudes from the front of the housing 8 in any suitable manner so that the shaft l1 may be readily rotated to cause it to be moved in or out relative to the frontof the housing 8. The portion of the shaft 11 which protrudes from the bushing I8 toward the interior of the device 1 is knurled and also has a portion of its round surface flattened. This portion of the shaft is surrounded by a collar 19 having two projections 20 and 2| spaced slightly less than 180 degrees apart. These projections :28 and 2i are arranged to engage a projection 22 extending toward the interior of the housing 8 so as to limit the rotation of the shaft 13 to substantially one-half of a revolution. In threaded engagement with the inner portion of the shaft I1 is a. threaded screw 23 having a round head which projects toward the interior of the housing 8 from the inner end of the shaft. With the construction so far described, it will be observed that rotation of the knob l8 in one direction causes the rounded head of the screw 23 to move toward the back of the housing 8 and rotation of the knob 18 in the opposite direction causes the rounded end of the screw 23 to move toward the front of the housing 8.

The rounded end of the screw 23 engages a rectangular-shaped plate 24 of insulating material, one end of which, together with one end of a similar shaped brass plate 25 and one end of a bimetallic member 26 are riveted to a spring or flexible support 21, which in turn is secured to the inner side of the housing 8 by screws 28. The free end of the bimetallic member 26 carries a contact 29 which is arranged to engage a stationary contact 30 mounted near the end of one of the arms of an L-shaped member 3| of flat conducting material, such as brass, which is fastened to the housing 8 by a screw 32. Movement of the screw 23 as a result of rotating the knob l8 therefore flexes the spring support 21 so as to vary the position of the bimetallic member 26 and contact 29 with respect to the fixed contact 30. When the screw 23 is moved toward the back of the housing 21 in response to rotation of the knob l8, the screw 23 increases the temperature setting of interior of the housing so that the temperature the device, whereas when it is moved in the opposite direction, the temperature setting of the device is reduced.

In order to obtain a snap opening and closing of the contacts 23 and 36, the stationary contact 36 comprises a small U-shaped permanent magnet 33, preferably an alnico mag'net, soldered or otherwise secured to the member 3| and a flat contact 34 of suitable non-magnetic material such as silver, soldered or otherwise secured across the two pole faces of the magnet 33. The movable contact 29 is made of suitable magnetic material, such as steel, on which is secured by any suitable means, such as rolling or welding, a sheet of suitable contacting material, such as silver, so that a silver-to-silver contact is obtained when the contacts 23 and 36 are in engagement.

In order to obtain the proper temperature differential of operation, the stationary contact 36 is secured to the member 3| which is moved relatively to the movable contact 26 so as to change the amount of flux threading the magnet 33 and the magnetic material in the movable contact 29 to the proper amount to produce the desired calibration. Then member 3| is securely anchored by screw 32 at the position thereon that produces the proper calibration.

In order to materially reduce the effect on the temperature of the bimetallic member 24 of any are established between the contacts 26 and 36, such heating effect is localized at the free end of the member 24 by restricting the cross-section of the portion of the member 26. This result is obtained in the arrangement shown by providing the holes in the bimetallic member 26 just above the contact 21 so that the thermal resistance between the contact 23 and the main body of the member 26 is high.

A small electric heater 36 of any suitable type is fastened to the inner surface of the portion of the housing 6 which constitutes the front of the heat control device I by suitable means, such as the screws 36. As shown, the heater 36 is arranged in the form of a coiled heater (not shown) encased within a hollow porcelain cylinder through which passes one of the leads 3! that supplies current to the heater 36. This heater 36, which has a relatively high thermal time constant is so located between the bimetallic member 26 and the housing 6 that the heating of the bimetallic member 26 varies in accordance with the current flowing through the heater 36.

In the lower portion of the housing 6 is located my improved manually operated switch for opening and closing the circuit through the heating device whose temperature the control device I is arranged to control. This switch comprises a flat spring contact member 36 which is arranged to be moved into and out of engagement with a stationary contact 36 secured to the other arm of the L-shaped member 3| than the one to which the stationary contact 36 is secured. The spring contact member 36 comprises a spring blade, one end-of which is secured to the inner surface of the housing 6 by a screw 46 and the other end of which has a contact 4| secured thereto. The spring member 36 is arranged to be flexed by means of a cam and operating trigger member 42 of suitable molded insulating material and provided with proi ecting cylindrical sections 43 which rotate in the housing 6. The trigger section of the member 42 consists of two sectors 44 and 46 which extend through an opening in the front of the housing 6 and which are so arranged that counter-clockwise rotation of the trigger member causes the sector 44 to protrude from the front of the housing, whereas clockwise rotation of the trigger member causes the sector 46 to protrude from the front of the housing. One of these sectors, such as 44 for example, may be painted or otherwise marked in any suitable manner so that the condition of the switch contacts may be readily observed merely by observing the color or the mark on the sector that protrudes from the front of the housing.

The cam section of the member 42 comprises a flat portion 46 arranged to be substantially parallel to the spring member 36 when the latter is in the open circuit position, as shown in Fig. 4, and another flat portion 41 which is arranged to be substantially parallel to the spring member 36 when the latter is in its closed circuit position, as shown in Fig. 5. The member 42 also has a semispherical surface 46, preferably of steel, projecting from its surface at a point intermediate the two flat surfaces 46 and 41 and which moves into a hole 46 in thespring member 36 when it is in its open circuit positioiishown in Fig. 4.

The normal tension of the spring member 36 causes it to press forcibly against the member 42 at all times, and therefore it firmly maintains the trigger member 42 in each of its two positions. The semispherical surface 46 and the two cam surfaces 46 and 41 are 50 located on the trigger member 42 that when the trigger member 42 is in the position shown in Fig. 4 the normal tension of the spring member 36 against the cam surface 46 opposes counterclockwise movement of the trigger member 42 and the normal tension of the spring member 36 against the semispherical surface 46 opposes clockwise rotation of the trigger member 42, and when the trigger member 42 is in the position shown in Fig. 5 the normal tension of the spring member 36 against the cam surface 46 opposes clockwise movement of the trigger member 42 and the normal tension of the spring member 36 against the semispherical surface 46 opposes counterclockwise rotation of the trigger member 42. The member 42 is held within the housing 6 by an anchor plate 66 secured to the housing by the screws 6| which anchor plate bears against the cylindrical sections 43 of the trigger member 42 thereby confining them within the bearing sections of the housing. The anchor plate 66 also has an extension 62 containing an opening 63 through which the spring member 36 extends. The top edge of the opening 63 acts as a fixed fulcrum point for the spring member 36 so that when the center section of the spring member is forced upward and away from the flat portion 46 of the cam member 42 by the semispherical member 48 moving out of the hole 49 and under the spring member 36 and by the positioning action of the surface 41 of cam 42 when the trigger member 42 is rotated clockwise from the position shown in Fig. 4, the free end of the spring member 36 is deflected downwardly so that the contact 4| on the spring member 36 engages the stationary contact 36, as shown in Fig. 5. Similarly, when the trigger member 42 is rotated in a counterclockwise direction from the position shown in Fig. 4, the semispherica] member 46 moves from under the spring member into the hole therein so that th normal tension of the member 36 causes the center portion thereof to move downwardly and the free end thereof to move upwardly about the edge of the opening 63 as a fulcrum so that the contact 4| is moved out of engagement with the stationary contact 33.

The control device I is arranged to be connected in the electric circuit to be controlled thereby by establishing a connection to a terminal 64 which is secured to and in electric conover any given interval of time.

tact with the bimetallic member spring support 21 by one of the screws 25 and a connection to a terminal 55 which is secured to and in electrical contact with one terminal of the heater 35 by one of the screws 56. The electric connections of the various elements of the control device I will be more clearly seen from the diagram shown in Fig. 6 which illustrates a control system for an electric blanket embodying my control device. In this Fig. 6, 55 represents an electric blanket having a heating resistor 51, the ends of which are connected to a pair of terminal pins 58 that are adapted to be enof which is connected to a supply plug 52 through the contacts 39 and I are in engagement to the time that these contacts are out of engagement. These times are controlled by the temperature of the bimetallic element II, which is jointly dependent upon the room temperature and upon the heat supplied to the bimetallic element from the auxiliary heater 35. For a given unchanging room temperature, the bimetallic element controls the time of engage ment of the contacts 29 and 30 so as to maintain the temperature of, th blanket at a substantially constant value. When the room temperature varies, however, the amount of energy input into the blanket is varied since thus, if for a given setting of the control device. the room temperature should decrease, the heat that would be imparted to the bimetallic element 2! from the room is reduced and therefore vit raquires a longer period of time for the auxiliary heater 35 to heat the bimetallic member 26 to the temperature at which it causes the contacts 29 and 30 to disengage than it did before, and after these contacts have opened and the auxiliary heater 35 is deenergized, the thermostatic movement of the free end of said spring member;

element will cool quicker to caus the contacts to reengage due to the-increased cooling action of the room. These two action of delaying the separation of the contacts and in advancing their closing result in an increase in the proportion of time that the contacts are in engagement The control, therefore, supplies more energy to the blanket during a given time interval so as to maintain the temperature of the blanket at a predetermined value in spite of the decrease in room temperature. Conversely, when the room warms up, the proportion of time that the contact 29 and 30 are in engagement to the time that they are out of engagement is decreased so as to decrease the total amount of energy supplied to the blanket during a given tim interval.

The transformer 6i functions to reduce the voltage of the supply line to a relatively low value so as to eliminate any danger of shock by the user of the blanket.

While I have, in accordance with the .patent statutes. shown and described my invention as applied to a particular construction and as embodying various devices. changes and modifications will be obvious tothose skilled inthe art, and'I therefore aim in the appended claims to coverall such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States. is:

1. In combination, a housing, a flat spring member having one end thereof fastened to said housing, a stationary fulcrum engaging one side of said spring member-intermediate the ends thereof, a rotatable member mounted in said housing and having a cam surface in engagement with the other side of said spring member at a point between said fulcrum and the fastened end of said spring member, said cam surface being so shaped that rotation of said rotatable member in one directionflexes said spring member in a predetermined direction to effect movement in the opposite direction of the free end of said spring member and also so shaped that it engages said spring member at different points so that said spring member exerts opposing forces on said rotatable member, and cooperating contacts controlled by the movement of the free end of said spring member.

2. In combination, a housing, a flat spring member having one end thereof fastened to said housing, a stationary fulcrum engaging one side of said spring member intermediat the ends thereof, a rotatable member mounted in said housing and having a cam surface in engagement with the other side of said pring member at a point between said fulcrum and the fastened end of said spring member and having a projection extending into .an opening in said spring-- member and arranged on movement of said rotatable member in a predetermined direc tion to be moved out of said opening and under said spring member whereby said spring member is flexed in a predetermined direction to effect said projection and said cam surface being so located on said rotatable member that said spring member respectively exerts opposing forces against said projection and said cam surface; a contact carried on the free end of said spring member, and a cooperating stationary contact secured to'said housing.

3. In combination, a housing, a flat spring member havingone end thereof fastened to said housing, a stationary fulcrum engaging one side of said spring member intermediate the ends thereof, a rotatable member mounted in said housing and having a cam surface in engagement with the other side of said spring member at a point between said fulcrum and the fastened end of said spring member and having a semispherlcal projection extending into a hole in said spring member and arranged on movement of said rotatable member in a predetermined direction to be moved out of said hole and under said spring member whereby said spring member is flexed in a predetermined direction to effect movement of the free end of said sp in member. said projection and said cam surface being so located on said rotatable member that when said projection is in said hole said spring member exerts against said projection a force which opposes movement of said rotatable member in said first-mentioned predetermined direction and exerts against said cam surface a force which opposes movement of said rotatable member in the opposite direction and when said projection is moved out of said .hole'said spring member exerts against said projection a force which opposes movement of said rotatable member in aid opposite direction and exerts against said cam surface a force which opposes movement of said rotatable member in said first-mentioned predetermined direction, a contact carried on the free end-of said spring member, and a cooperating stationary contact secured to said housing.

4. In combination, a housing, a fiat spring member having one end thereof fastened to the inside surface of said housing; a stationary fulcrum engaging one side of said spring member intermediate the ends thereof, a cam and trigger member rotatably mounted inside said housing and having the trigger portion thereof extending through an opening of said housing whereby said cam and trigger member may be manually rotated, the cam portion of said cam and trigg r member having a semispherical projection extending into an opening in said spring member at a point intermediate said fulcrum and the fastened end of said spring member and arranged on movement of said cam and trigger member to be moved out of said opening and under said spring member to flex said spring member to efl'ect movement of the free end of said spring member, said projection and said cam surface being so located on said rotatable member that when said projection is in saidhole said spring member exerts against said projection a force which opposes movement of said rotatable member in a direction to effect said movement of said projection out of said hole and exerts against said cam surface a force which opposes movement of said rotatable member in the pposite direction and when said projection is moved out of said hole said spring member exerts against said projection a force which opposes movement of said rotatable member in said opposite direction and exerts against said cam surface a force which opposes movement of said rotatable member in said first-mentioned direction, and cooperating contacts controlled by the movement of the free end of said spring member.

5. In combination, a housing, a flat spring member having one end thereof fastened to the inside surface of said housing, a stationary fulcrum engaging one side of said spring member intermediate the ends thereof, a cam and trigger membe rotatably mounted inside said housing and having the trigger portion thereof extending through an opening of said housing whereby said cam and trigger member may be manually rotated, the cam portion'of said cam and trigger member having a semispherical projection extending into an opening in said spring member at a point intermediate said fulcrum and the fastened end of said spring member and arranged on movement of said cam and trigger member to be moved out of said opening and under said spring member to flex said spring member to effect movement of the free end of said spring member, cam surfaces on the cam portion of said cam and trig er member respectively arranged to be engaged by said spring member when said semispherical projection is in said opening and when said projection has been moved to a predetermined point under said spring member, said projection and said cam surfaces being so located on said rotatabl member that when said projection is in said hole said spring member exerts against said projection a force which opposes movement of said rotatable member in a direction to effect said movement of said projection out of said hole and exerts against one of said cam surfaces a force which opposes movement of said rotatable member in the opposite direction and when said pro- J'ection is moved to said predetermined point unde said spring member said spring member exerts against said projection a force which opposes movement of said rotatable member in said opposite direction and exerts against the other cam surface a force which opposes movement of said rotatable member in said first-mentioned direction, a stationary contact, and a contact carried by the free end of said spring member arranged to engage said stationary contact when said projection is in said opening and to be moved out of engagement with said stationary contact when said projection is moved to said predetermined point under said spring member.

LEONARD W. COOK.

. csnmmcm: or CORRECTION. Patent No. 25 1;,910. August 1, 19m.

- momma w. 0001:.

It is hereby certifie'd that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 6l4., before "Fig. )4." insert --Fig. 5to the position shcwn in--; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the recordef the case in the Patent Office.

Signed and sealed this 26th day of .September, A. D. 191414.

Leslie Frazer (Seal) Acting Commissioner of Patents.

, CERHFICATE OF commcmon. A r Patent No. 2,55L 91o. August 1, 19%.

- LEONARD w. COOK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, sec- 0nd column, line fin, before "Fig. 1 insert "Fig. 5to the position shown. in"; and that the said Letters Patent should be read with this correction therein that the same may conform to the recorder the case in the Patent Office. I

Signed and sealed this 26th day of .September', A D. 19%.

Leslie Frazer (Seal) 1 Acting Cominissioner of Patents. 

